Nowadays, some portable telephones are provided with a function that is able to call directly to the other party from the display of a telephone book list in which telephone numbers and names of other parties have been registered, namely, a telephone book list function. Generally, an input device such as a ten-key keypad has been used for entering information to this telephone book list.
By the way, a portable telephone progressing in miniaturization and light-weight is running short of even a space for mounting an input device such as a 10-ten key keypad. Therefore, it is required to realize an input device which can manage with less mounting space